1. Field of the Invention
The present invention relates to a diamine, and also to polymers such as polyamides, polyimides and poly(amide-imide)s polymerized therefrom.
2. Description of the Prior Art
Aromatic polyamides and polyimides are well known as high-performance polymers, which possess excellent thermal stability, inert behavior against organic solvents, and good mechanical properties. Although wholly aromatic polymers have a higher melting point and a higher heat resistance than aliphatic polymers. However, as their rigid structures cause high softening temperature and poor solubility to many organic solvents, it was often difficult to fabricate them. For instance, wholly aromatic polyamides are insoluble in organic solvents without the aid of a solution promoter such as LiCl or CaCl.sub.2, and such polyamides have no softening point and hence, are infusible. Accordingly, their application is considerably limited. Thus, the improvement of their processability has been extensively investigated.
One of the successful approaches to increase solubility of polyamides and polyimides is the introduction of flexible linkages into polymer backbone. For instance, the incorporation of flexible linkages, such as arylene ether (--O--) [EP 0565352 A2, JP 05262705], methylene (--CH.sub.2 --) [EP 0483954 A1], sulfone (--SO.sub.2 --) [JP 05295262], isopropylidene [--C(CH.sub.3).sub.2 --] [U.S. Pat. No. 4,410,684, JP 04183721], and siloxane (--Si--O--) [JP 052141000, JP 04189867] into the polymer backbone to increase the overall chain flexibility.